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Spin injection in semiconductor nanowires for future spin based computing

Jülich, September, 2012: In contrast to conventional electronics, where the electric charge is used for switching purpose, in spin electronics the magnetic property of the electron, its spin, is employed. It is expected that spin-based transistors outclass conventional transistors regarding speed and power consumption.

Group III-V semiconductors, consisting of a group III and group V element, e.g. InAs, are very suitable for spin manipulation, due to their intrinsic property known as spin-orbit coupling. In particular quasi one-dimensional nanowires made of this material are expected to show enhanced electronic device properties. Researchers at the Peter Grünberg Institute and RWTH Aachen University have accomplished an important step toward nanowire spin logic and report on their findings in Nano Letters.

For their experiment, semiconductor nanowires made from indium nitride were chosen. The diameter of these nanostructures is typically about a factor of thousand smaller than a human hair. The researchers had to conceive a totally new preparation method, which results in the horizontal nanowires to be halfway embedded in a surrounding dielectric. Magnetic cobalt electrodes with delicate interface properties are utilized to drive a current into the semiconductor nanowires. Owing to the magnetization of the cobalt electrodes the current drags along the spin polarization into the otherwise nonmagnetic nanowire. At low temperatures few degrees above absolute zero, magnetic fields are used to alter the magnetization of the electrodes on top of the nanowire independently. Due to the proximity of the two magnetic contacts on top of the nanowire the second magnet “sees” the spin-polarization of the electrons diffusing in the nanowire. The results obtained here are an important step forward on the route toward prospective energy-saving one-dimensional devices for spin-based computing.

Left: Spin injection device with an indium nitride nanowire halfway embedded into a dielectric medium and electrically contacted with two cobalt-tunnel-contacts for spin injection and detection, respectively. Nonlocal spin valve measurements were performed (right) which conclusively demonstrate injection of spin polarized currents into the nanowire with an intrinsic depolarization length of about 200 nm. Copyright: Nano Letters